The present invention relates to encoding and decoding broadcast or recorded segments such as broadcasts transmitted over the air, via cable, satellite or otherwise, and video, music or other works distributed on previously recorded media, as well as monitoring audience exposure to any of the foregoing.
Broadcast segments include live programs, taped programs, commercials and the like. These segments may be aired according to a wide variety of schedules, for example, national coverage, particular geographic coverage or to fill otherwise unreserved programming slots. Furthermore, the scheduled broadcast time may be uniform nationwide or vary according to a broadcaster's local considerations.
There is a need to independently detect when segments, such as commercials, were actually broadcast over a given channel or by a given station.
There is also a need to monitor the audience for broadcast segments because rates charged for broadcast typically depend on audience size. Further, some market research techniques involve testing the effect of broadcast segment frequency and/or nature on consumer purchase decisions.
There are several conventional methods of detecting the identity of broadcast segments. However, each of these methods is limited in at least one respect, such as its complexity, its intrusiveness or inconvenience to audience members, or its vulnerability to errors caused by a noisy environment.
In one such method, each of a number of selected audience members maintains a diary of which programs he or she viewed or heard. This method relies on the voluntary and timely cooperation of the selected audience members. Advertisers, advertising agencies and broadcasters have in the past expressed concerns that media experiences may not have been fully reported by respondents in their diaries. In particular, it has been inferred from survey data that the media experiences of young children, teens and young men are especially underreported. It is thought by some that such groups are either unable to complete the written diaries or find this task to be particularly tedious and thus neglect to enter complete information.
To avoid the perceived drawbacks of manual recording, passive recording methods have been sought. Such passive recording methods would be characterized by the presence of a device which attempts to sense, in real time, the broadcast segments to which an audience member is exposed and record this information, which would later be retrieved at or uploaded to a centralized data processing facility. Since the information would be collected in computer readable form, data processing could be carried out readily with the use of a passive recording apparatus. Information collected by passive recording would be free of human error, and in this respect would enjoy improved reliability.
Devices known as "personal passive people meters", which are small and portable, have been proposed. Such devices are intended to be carried by persons whose broadcast segment exposure would be monitored. These meters would permit viewer/listener determination at the individual level, which is highly desirable.
A major problem in passive recording is to correctly sense the segment to which a viewer is being exposed. The proposed approaches involve attempting to identify both unmodified broadcast segments, and segments modified before broadcast to make them more readily identifiable.
One approach to identification of unmodified segments involves pattern recognition. Each segment is analyzed before or after broadcast and its analyzed characteristics determine its "broadcast signature". A table of broadcast signatures is created by, or made available to, each monitoring station. In operation, a monitoring station attempts to analyze the characteristics of a segment being broadcast and match it to one of the broadcast signatures, that is, recognize its pattern. This approach uses relatively complicated technology and is cumbersome to implement due to the need to enable each monitoring station to recognize new segments as they are introduced.
Several identification approaches involve modifying the broadcast segments to provide a code which the detecting equipment is designed to recognize. An advantage of these approaches is that the monitoring stations need not be updated as new broadcast segments are created.
U.S. Pat. No. 3,004,104 (Hembrooke) proposed to suppress a narrow band of frequencies (10 Hz wide) in a portion of the voiceband (1000 Hz) at timed intervals according to a predetermined code. However, if the suppression is short enough to be imperceptible as information to an audience member, then the suppression may be susceptible to interference from ambient noise sources.
It has also been proposed to modulate the audio frequency subcarrier with an identifying code of narrow bandwidth (100 Hz) and short duration (3 seconds) at the start and end of each segment. This technique is unsatisfactory because the metering equipment for a viewer or listener who tunes in a moment too late and tunes out a moment too early fails to sense the identifying code, and because it is vulnerable to noise.
It has been proposed in the alternative to mix subaudible-frequency identifying codes with conventional audio in the program segments. This technique assumes the monitoring station would receive the broadcast, prior to audible reproduction by the reception equipment, since some reception equipment is of poor quality and might not reproduce this information with sufficient fidelity for a personal metering device to recognize it. Thus, this technique is unsuitable for a personal meter of the type which monitors acoustic signals.
A technique proposed for use with a musical recording comprises eliminating a sequence of six frequency bands from an audio signal, with the sequence varying during the course of the signal, and in place of the eliminated frequencies, inserting a sequence of code signals. This technique can be circumvented, since it is fairly easy to remove the included signals. Further, this technique is vulnerable to noise, especially acoustic noise.